SolarWindow™ is a novel photovoltaic window technology, based upon organic photovoltaics, that is the subject of several separate patent filings. This technology has numerous benefits when implemented independently, including the ability to generate power yet retain a high level of visible light transmission (VLT) in an attractive window application. This technology also allows the absorption of infrared (IR) light, thereby reducing the solar heating of buildings and individuals inside the buildings, increasing user comfort and decreasing building HVAC costs.
One limitation of the SolarWindow™ technology, however, is the static nature of its VLT; on a very bright, sunny day the total amount of visible light transmitted is greater than on darker/cloudier days, since the percentage of VLT does not change. As a result, visible-light based solar heating of buildings and window end-users, as well as discomfort from increased glare, will not be substantially reduced on such days. Electrochromic windows, on the other hand, allow the degree of VLT to be altered, permitting users to control visible-light based solar heating and glare on sunny days, or for privacy reasons.
Electrochromic windows, of all types, have a number of limitations, however, that are currently preventing their large-scale commercial application. Because electrochromic windows rely on electricity to switch their states from high-to-low VLT and vice-versa, such windows must be directly tied into the building infrastructure. This significantly increases the cost of implementing electrochromic windows, even though the total electricity usage and costs are minimal. Furthermore, electrochromic windows do not generally absorb IR light, so they do not prevent a major source of solar heating of buildings and users, and thus require further ‘low-e’ coatings to control IR transmission.